If avatar is rotated (transformed) to 45 degrees by Z (or otherwise any other angle not divisible by 90) for instance, it is really hard to move bones straight (in respect to avatar - local).
Have to do numerous tweaks before you get the bone to the right position, or use a gizmo plains, which are also not precise and hard to use.

Please add a "Local Move" for the bones and make our life easier!